Numerous studies have documented racial differences in deaths from cancer among non-Hispanic whites and African Americans, but little has been known about survival outcomes for Asian Americans who have been diagnosed with cancer, until now. A new study from Dr Quoc-Dien Trinh and colleagues at Brigham and Women's Hospital examined cancer patients in eight different Asian American subgroups and found their cancer-specific mortality was substantially lower than that of non-Hispanic white patients. The findings are published in the March 20 issue of the Journal of the National Cancer Institute (JNCI).
Racial disparities in cancer survival outcomes have been primarily attributed to underlying biologic mechanisms and the quality of cancer care received. Because prior literature shows little difference exists in the socioeconomic status of non-Hispanic whites and Asian Americans, any difference in cancer survival is less likely to be attributable to inequalities of care, explained the authors in the study background.
"What we have found is that Asian Americans are an incredibly diverse group that cannot be indiscriminately combined together," said Dr Trinh, associate surgeon for the Division of Urology at Brigham and Women's Hospital, faculty at the Center for Surgery and Public Health and lead author of the study. "With Asian Americans, there is important variation in socioeconomic status, cultural beliefs, and length of time since immigrating to the United States that researchers must take into account."
Although Asian Americans represent only 5% of the entire United States population, they are the most rapidly growing racial group in the country. This is one of the first studies not just to focus on the cancer-specific survival of Asian Americans, but also to break down that population into eight specific subgroups: Chinese, Filipino, Hawaiian/Pacific islander, Japanese, Korean, South-East Asian – Indian/Pakistani, Vietnamese and other Asian for further analysis.
Dr Trinh and his colleagues used Surveillance, Epidemiology, and End Results Program (SEER) data to look at more than 2.5 million Asian American patients who were diagnosed with lung, breast, prostate or colorectal cancer (the three leading causes of cancer-related mortality within each gender) between 1991 and 2007.
The team found significant differences in cancer outcomes among the Asian subgroups. Specifically, the researchers report that the Japanese subgroup had substantially better survival rates than non-Hispanic whites (especially with regard to prostate, breast and colorectal cancers), as did those of Filipino and South Asian descent (for prostate and lung cancers, and lung and colorectal cancers, respectively), while the Hawaiian and Korean subgroups did not. In Chinese and Vietnamese patients, only those with lung cancer had better cancer-specific mortality rates relative to non-Hispanic whites. Overall, most Asian subgroups were less likely to die from cancer than non-Hispanic white patients.
The authors found that cancer-specific mortality is statistically significantly lower for Asian Americans than for non-Hispanic whites overall, despite similarities in odds of receiving definitive therapy, and even after adjusting for socio-demographic factors, cancer stage and treatment. "We've effectively ruled out a number of variables, suggesting instead that underlying genetic or biological differences and/or complex cultural influences may impact survival in Asian American cancer patients", said Dr Trinh.
This study opens the door for future research to better understand why Asian Americans have better cancer-specific mortality than non-Hispanic whites, and to determine whether and to what extent genetic and/or cultural factors are involved.
The study was supported by an unrestricted educational grant from the Vattikuti Urology Institute and the Professor Walter Morris-Hale Distinguished Chair in Urologic Oncology at Brigham and Women's Hospital.
Reference
Trinh QD, Nguyen PL, Leow JJ, et al. Cancer-specific mortality of asian americans diagnosed with cancer: a nationwide population-based assessment. J Natl Cancer Inst 2015; Advanced online publication 20 March. doi: 10.1093/jnci/djv054.